Safety governor for pneumatic tool



Oct. 18, 1966 LE N 3,279,485

SAFETY GOVERNOR FOR PNEUMATIC TOOL Filed April 22, 1963 INVENTOR. 73ROBERT H. ALEXANDER 25 76 $6 78 wmlgww ATTORNEYS United States Patent M3,279,485 SAFETY GOVERNOR FOR PNEUMATIC TOOL Robert H. Alexander,Dayton, Ohio, assignor to Rockwell Manufacturing Company, Pittsburgh,Pa., a corporation of Pennsylvania Filed Apr. 22, 1963, Ser. No. 274,5104 Claims. (Cl. 137-50) This invention relates to pneumatic tools havinga rotary drive, particularly to such tools used as grinders or the like,and wherein a governor, usually centrifugally operated, controls thespeed of the motor.

In such tools, particularly when used to rotate grinding wheels, it isdesirable to prevent overspeeding of the rotary motor. This might occur,for example, if there was a malfunction of the governor mechanism, ascan occur due to dirt, wear, or some other reason which causes thegovernor to stick. When these devices overspeed it is possible quicklyto exceed the safe speed of rotation of the grinding wheel, and as aresult centrifugal force will cause the wheel to disintegrate, withobvious dangerous results.

The present invention provides a novel safety governor mechanism whichcomes into operation only in the event that the rotary motor exceeds thespeed range under which it normally operates due to the regular governorcontrol. If such excessive speed occurs, the present invention providesa quick-acting safety governor mechanism which will immediately cut offthe air flow to the motor, or in any event at least so greatly impedethis air flow that the motor will be stopped or slowed too far below itsoperating speed, thereby avoiding the undesirable and dangerousconditions as mentioned previously.

Accordingly, the primary object of this invention is to provide a safetygovernor mechanism for a pneumatic tool having a rotary motor, and inwhich the driving fluid to the motor enters through an inlet port,wherein a safety valve member is mounted upstream of such port withrespect to the motor, and is held in this position by a latch which inturn holds the valve against the bias of a spring or equivalent deviceurging the safety valve toward the port to block passage of motive fluidthrough it, and wherein an adjustable centrifugally operated safetyrelease device is connected to the latch for releasing it in response tooverspeeding of the motor.

Another object of the invention is to provide such a safety governorconstruction which may be adjusted to release the latch at apredetermined speed which is in excess of the normal governed speedrange of the tool.

A further object of the invention is to provide such a safety governorconstruction wherein the parts including the latch, its biasing orvalve-closing means, and the centrifugally operated safety release, canall be incorporated within the regular governor mechanism, and can beapplied to the tool as a part of the governor device.

Another object of the invention is to provide a novel safety governormechanism which is of simple and relatively inexpensive construction,but which is reliable in its operation such that it will avoidoverspeeding of the motor even though it may be called upon to functionin this manner only upon rare occasions.

Other objects and advantages of the invention will be apparent from thefollowing description, the accompanying drawing and the appended claims.

In the drawing FIG. 1 is a view, primarily in section and with someparts broken away, taken .thorugh a typical pneumatic tool of the type,showing the governor mechanism and the safety governor construction inits general relation to the other parts of the tool;

FIG. 2 is a substantially enlarged longitudinal section 3,279,435Patented Get. 18, 15966 View taken through the governor and the safetygovernor mechanism incorporated therein;

FIG. 3 is a view similar to FIG. 2, but with the parts moved toillustrate the closed position of the safety valve, which it attainsupon functioning of the safety governor mechanism;

FIG. 4 is an end view of the governor mechanism per se, as seen from theend thereof attached to the motor shaft;

FIG. 5 is a sectional view taken on line 55 of FIG. 4-; and

FIG. 6 is a detail view, taken on the line 6-6 of FIG. 3, showingportions of the latch mechanism of the safety governor in the releasedposition thereof.

Referring to the drawing, which illustrates a preferred embodiment ofthe present invention, a typical pneumatic rotary grinding machine ofthe portable type is shown as including a main body or housing 10 withinwhich there is a conventional rotary pneumatic motor 12, of the slidablevane type, and which has its output shafts or ends mounted in bearings13 fore and aft of the main body. The forward portion of the shaftextends outwardly of the body and provides an arbor indicated generallyat 15 upon which a grinding or abrasive wheel, or some other rotarytool, is to be mounted. On the rear of the motor shaft, behind the aftbearing 13, there is mounted the governor mechanism, shown generally at20, and housed within the motor air plenum chamber 22. Air from thischamber passes through the inlet opening 23 in the housing to the motor12. Air is admitted to the chamber through an inlet port, shown as aninserted port member 25.

This air is received through a supply passage 27 which leads from amanually operable valve 28 carried in the usual manner within the handle30 of the tool. This handle is likewise provided with an inlet passageupstream of the valve, and motive fluid such as air under pressure issupplied through the hose or tube 32 coupled to the handle.

The governor mechanism, particularly with reference to FIG. 2, includesa main body 35 having a threaded stem 36 which is threaded into the rearor aft end of the rotor portion of the motor, a segment thereof beingshown at 37. The governor body includes radially extending arm portions38, which are hollow, and, displaced approximately from these arms,radially extending fiyweight support arms 39 which are shown in FIGS. 4and 5.

Between these flyweight support arms there are centrifugally responsivegovernor weights 40, each of which is mounted for pivotal movement on apin or rod 42 extending between adjacent arms 39.

The rearward portion of the body 35 terminates in a threaded end 45 ofreduced size, and a spring stop 47 is fastened thereon. Abutting thisstop is the main governor spring 50 which acts between the stop and thecylindrical governor valve member 52. This valve member has appropriateslots therein to pass around the arms 38, and to pass between the arms39, whereby the inwardly extending tips 53 of the weights 40 arearranged to press against the valve 52, and to urge it toward the inletport 25 against the force of spring 50. In other words, this is a moreor less conventional type of proximity governor apparatus, another formof which is shown in the patent to Conklin et al., No. 2,925,089 issuedFeburary 16, 1960, and presently assigned to the same assignee as thisapplication.

The safety governor mechanism, which is the feature of the presentinvention, includes a safety valve member 60, fixed to the end of a rodor shaft 62 which is in turn mounted for sliding movement in alongitudinal bore or passage 63 formed in the main governor body 35.Preferably, the valve member 66 includes a compressible seal such as anO-ring 64 carried about its periphery to assure a good cut-ofl actionbetween this valve and the inlet port 25. It should be understood,however, that this seal is unnecessary, and in fact a complete closingof the port is not essential, so long as the safety valve member is ofsulficient size to provide an effective throttling of the flow of motivefluid to such an extend that the motor cannot operate at its normalspeed.

The portion of the rod 62 which extends across the passage or opening 65through the arms 38 is provided with a slot or similar recess 66. Thisrecess cooperates with a latching slide 68 to form the releasable latchmechanism normally operating to hold the valve 60 in an open position,upstream of the port 25. The valve is preferably urged toward its closedposition, as shown in FIG. 3, by spring 76 which acts between the baseof a counter-bore 72 in the threaded forward end 36 of the governorbody, and a snap ring 73 or equivalent carried on the forward end of therod 62. It will be obvious from inspection of the drawings andcomparison of FIGS. 2 and 3, that when the latching slide 68 is movedradially outward to disengage from the slot 66, spring 7% will tend tocarry the valve 60 into a closed position with respect to the inlet port25.

The slide 68 constitutes a safety flyweight, which can move radiallywithin that one of the arms 38 in which it is mounted. The slide ishollow, and the side walls thereof are provided with transverselyaligned slots 76, as shown in FIG. 6, to permit passage of an anchor pin78 which will define the position of the slide without interfering withits sliding motion. A spring 80 is positioned within slide 68, and abutsat one end the pin 78, and at the other end a threaded set screw 82.This screw can be adjusted, for example by insertion of a suitablewrench within the socket 83 in its head, to adjust the loading of spring80 in its normal position. I

As previously mentioned, the parts during normal operation are in theposition shown in FIG. 2. The slide 68 is engaged within slot 66 therebyholding the safety valve member 60 in open position against the ungingof spring 70 and the force of the pressure air flowing into the port 25.If for some reason the main governor mechanism does not Work and themotor overspeeds, the resultant centrifugal force acting on the slide 68will be suflicient to overcome the force of spring 80, which has beenappropriately preset, and the slide will move radially outward torelease the valve rod or stem 62, whereupon it Will be urged to theright as shown in FIG. 3 carrying the valve 60 into the inlet port 25.

It should be noted that this action is in conjunction with the normalflow of air from passage 27 into and through the port 25, and it hasbeen found that this flow in itself is suflicient to cause the closingmovement of the safety valve member. However, the spring '70 isdesirable from a safety standpoint. Once the rod 62 has moved to carrythe notch 66 byeond the slide 68, approximately to the position shown inFIG. 3, the tool will no longer operate, since air flow through port 25will be blocked, either cut ofl or so severly limited that an adequatevolume of air will not be available to the motor, even for limitedoperation. As a result the operator will be unable to use the tool, andin order to reset the safety governor mechanism, it is necessary todismantle the tool and correct the condition, whatever it may be, thatcaused malfunctioning of the governor.

It will be obvious from the foreging description and the drawing, thatthe present invention provides a novel and effective safety governorconstruction which is of simple design, easily manufactured, and whichis incorporated into present types of governor constructions wherebythis unit may be employed in new types of tools, and may also be adaptedwith little modification to existing tools, since the only additionalspace occupied by the present 4- mechanism (as compared to earliergovernor types) is that space required for the valve head 6% in itsnormal open position on the upstream side of the inlet port.

While the method and form of apparatus herein described constitutes apreferred embodiment of the invention, it is to be understooclthat theinvention is not limited to this precise method and form of apparatus,and that changes may be made therein without departing from the scope ofthe invention which is defined in the appended claims.

What is claimed is:

1. A safety governor for a rotary fluid motor including means forming aninlet passage through which pressure fluid is supplied to drive themotor, means defining an inlet port in said pas-sage, a centrifugallyoperated rotatably driven governor including a valve cooperating withsaid port to control the flow of fluid through said port in relation tothe rotational speed of said governor, a safety valve member, meansmounting said valve member in said passage upstream of said portincluding a latch holding said valve member normally spaced from saidport against the flow of pressure fluid entering said port, and acentrifugally operated safety release mechanism rotatably driven withsaid governor and operatively connected to said latch to release thesame in response to overspeeding causing said safety valve member tomove toward said port to block the passage of fluid through said port.

2. A safety governor for a rotary fluid motor including means forming aninlet passage through which pressure fluid is supplied to drive themotor, means defining an inlet port in said passage, a centrifugallyoperated rotatably driven proximity governor including a valve downstream of and cooperating with said port to limit the flow of fluidthrough said port to maintain a predetermined operating range ofrotational speeds, a safety valve member, means mounting said valvemember upstream of said port and normally spaced from said port, meansoperative on said safety valve member urging it toward said port toimpede the passage of fluid through said port, and a centrifugallyoperated safety release mechanism operatively connected to said safetyvalve member to release the same in response to overspeeding.

3. Apparatus as defined in claim 2, wherein said governor includes arotatable body driven by the motor and mounted coaxially of said inletport, said safety valve member including a rod slidably mounted in saidbody and extending through said port, a valve head on said rod normallypositioned on the opposite side of said port from said body and spacedfrom said port to permit free inflow of air toward said governor, anormally compressed spring acting on said rod tending to move said valvehead toward said port, and wherein said release mechanism includes asauxiliary flyweight carried by said body and engaging said rod to holdsaid valve head in its normal open position against said spring.

4. A safety governor for a rotary fluid motor including means forming aninlet passage through which pressure fluid is supplied to drive themotor, mean-s defining an inlet port in said passage, 21 centrifugallyoperated rotatably driven governor including a proximity valvecooperating with said port downstream thereof to control the flow offluid through said port in relation to the rotational speed of themotor, a safety valve member, means providing a slidable mounting forsaid safety valve member including a latch holding said valve membernormally spaced upstream from said port, an adjustable centrifugallyoperated safety release mechanism operatively connected to said latch torelease the same in response to overspeeding, and means operativeagainst said latch urging said safety valve member toward said port toblock the passage of fluid through said port upon release of said latch.

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS Van Sittert 9176 Jimerson 9176 Jirnerson 9176 Maclay 9176WILLIAM F. ODEA, Primary Examiner.

5 JOSEPH H. BRANSON, JR., Examiner.

F. SADLER, Assistant Examiner.

1. A SAFETY GOVERNOR FOR A ROTARY FLUID MOTOR INCLUDING MEANS FORMING ANINLET PASSAGE THROUGH WHICH PRESSURE FLUID IS SUPPLIED TO DRIVE THEMOTOR, MEANS DEFINING AN INLET PORT IS SAID PASSAGE, A CENTRIFUGALLYOPERATED ROTATABLY DRIVEN GOVERNOR INCLUDING A VALVE COOPERATING WITHSAID PORT TO CONTROL THE FLOW OF FLUID THROUGH SAID PORT IN RELATION TOTHE ROTATIONAL SPEED OF SAID GOVERNOR, A SAFETY VALVE MEMBER, MEANSMOUNTING SAID VALVE MEMBER IN SAID PASSAGE UPSTREAM OF SAID PORTINCLUDING A LATCH HOLDING SAID VALVE MEMBER NORMALLY SPACED FROM SAIDPORT AGAINST THE FLOW OF PRESSURE FLUID ENTERING SAID PORT, AND ACENTRIFUGALLY OPERATED SAFETY RELEASE MECHANISM ROTATABLY DRIVEN WITHSAID GOVERNOR AND OPERATIVELY CONNECTED TO SAID LATCH TO RELEASE THESAME IN RESPONSE TO OVERSPEEDING CASING SAID SAFETY VALVE MEMBER TO MOVETOWARD SAID PORT TO BLOCK THE PASSAGE OF FLUID THROUGH SAID PORT.